Tmidazolidine-2-thione derivatives



United States Patent a French body corporate N0 Drawing. Filed Oct. 29, 1964, Ser. No. 407,886 Claims priority, application France, July 17, 1964,

12 Claims. in. 260-795) The present invention provides a new group of chemical compounds suitable for vulcanizing mixes of halogenated synthetic elastomers, more especially mixes based on chloroprene polymers.

It is known that these elastomers are simple to vulcanize with metal oxides alone such, for example, as the oxides of zinc, magnesium, and lead, or with mixed such oxides. However, under these conditions vulcanization progresses slowly and is incomplete so that the vulcanizates obtained have unsatisfactory technical properties.

On the other hand, it is known that the use of classic vulcanization accelerators, either by themselves or in mixtures, such as the guanidines and the thiurams, raises the vulcanization speed and improves the characteristic properties of the vulcanizates, but these accelerators are still incapable of achieving the desired level of vulcanization.

Other, more specific accelerators, have been suggested for the vulcanization of mixes containing chloroprene polymers, especially imidazolidine-Z-thione, alkylated or cycloalkylated thioureas, triazine derivatives, thiosemicarbazides, thioxamides and cyclic polyamides.

The use of some of these compounds improves the properties of the vulcanizates substantially, but, quite frequently, this is accompanied by a lesser facility and safety in the handling of the mixes prior to vulcanization. Users in fact know very well the tendency of mixes, especially those which contain a thiourea, to undergo pre-vulcanization. Inconveniences of this kind may occur in the course of the diverse operations involved in the processing of the mix prior to vulcanization, and this may sometimes result in very appreciable losses of material.

It has now been found that the derivatives of imidazolidine-2-thione of the general formula:

R H2C'CH3 N-CHz-N N-CH2N R2 i 1) where R and R may be identical or different and each represents a lower alkyl or a cycloalkyl radical and R may also be a hydrogen atom, or the grouping --NR R represents a heterocyclic residue, are especially valuable accelerators for vulcanizing mixes based on a polychloroprene or a chloroprene copolymer. The lower alkyl radicals referred to above contain 1 to 5 carbon atoms and include, more especially, methyl, ethyl, propyl, isopropyl, n-butyl or isobutyl residues. preferably mononuclear cycloalkyl groups whose ring contains more than 4 carbon atoms, and this radical maybe substituted, especially by lower alkyl groups such as methyl or ethyl. Specifically, there may be mentioned the cyclopentyl, cyclohexyl and cyclooctyl group.

The cycloalkyl radicals are The heterocyclic radicals represented by the grouping NR R include especially saturated mononuclear heterocyclic residues containing 5 or 6 ring atoms, one of which is the nitrogen atom joined to R and R and another of which may be oxygen or sulphur, the remaining atoms being carbon. The carbon atoms of these heterocyclic residues may also carry substituents such as methyl or ethyl groups. Specifically, there may be mentioned the morph-olino and the piperidino group.

The compounds of Formula I are new and are very valuable accelerators for the vulcanization of chloroprene polymers. The chloroprene polymers which may be used are homopolymers of chloroprene and copolymers containing at least 40% of chloroprene residues, obtained by copolymerizing chloroprene with one or several comonorners, such as acrylonitrile, butadiene, isoprene, dichloro-2,3-butadiene or styrene. The manufacture of chloroprene polymers of the kind concerned in the present invention has been described in various publications, more especially in Synthetic Rubber, John Wiley and Sons, New York, pages 76 7 to 793 (1954).

The new accelerators may be used in amounts varying according to the individual polymer concerned, or the mix to be treated, or the special desired results. In general, the amount used is advantageously from 0.5 to 5 parts by weight for every parts by weight of the chloroprene polymer. The unvulcanized mixes, containing one or more compounds of Formula I, are within the scope of the invention.

The vulcanizates obtained have in general outstanding mechanical properties. Their surface is free from blemishes, which is not always the case with known accelerators.

On the other hand, the use of the new accelerators is considerably facilitated by the fact that the crude mixes have a thermostability much greater than that of any mix used in the past, without this improved stability in any way slowing down the vulcanization rate at the temperatures at which the latter is performed.

The vulcanization operation is conducted at the conventional temperatures, preferably within the range from to 200 C. and, as mentioned above, it proceeds very rapidly.

The products of the Formula I can be prepared, in accordance with a feature of the invention, by reacting 2 mols of formaldehyde with 1 mol of imidazolidine-2- thione and 2 mols of an amine of the formula HNR R The reaction can be represented as follows:

ZHN

The process is very simple to perform by adding formalin to a mixture of imidazoline-2-t'hione+amine in water at room temperature (15 to 25 C.) or with gentle heating, for example at about 50 C.

The following examples illustrate the invention.

Example 1 51 g. (0.5 mol) of imidazoline-Z-thione are made into a paste with a small amount of water, and the product is then dispersed in 300 cc. of water; 85 g. (1 mol) of piperidine are added and, at a temperature of 25 C., there are gradually added with stirring within /2 an hour 101 g. of formalin (corresponding to 1 mol of formal- N,N' bis (N-methyl-N-cyclohexylaminomethyl) imidazolidine-Z-thione, melting at 64 C.

Example 4 The following four mixes are prepared under the usual conditions in a roller mixer:

TABLE 1 Mix 1 2 3 4 l A known accelerator used for comparison.

With each of these four mixes the scorching time according to Mooney is measured, whereupon the mixes are moulded in a press at 153 C. The scorching time and the properties of the vulcanizates are shown in the dehyde). Towards the end of the addition of formalin following table:

TABLE 2 Searching time according to Vuleamsatmn Tensile Modulus Elongation Shore Appearance Mix Mooney at time in strength, 600%, at rupture hardness of surface 130 C. in minutes kgJcrn. kg./cm. in percent A minutes 1 Not vulcanized after 90 minutes 2 17 20 191 49 785 44 }Very slightly 40 187 64 745 ranular 3 45 20 195 49 790 43 g a a a r the temperature rises to 38 C. The batch is heated for 7 hours at 50 C., then cooled, filtered, and the filter residue is washed with water and dried in a ventilated drying oven at 50 C. In this manner there are obtained 143 g. of crude N,N-bis(piperidinomethyl)imidazolidine-Z-thione melting at 127 C. which is recrystallised from a hot solution in 400 cc. of acetone, and then allowed to cool to 15 C. The crystalline product is isolated by filtration, washed with 2X50 cc. of acetone cooled to 15 C., and dried, to yield 136 g. (=92% of theory) of recrystallised product melting at 127 C.

Example 2 The procedure described in Example 1 is repeated, ex cept that piperidine is replaced by 1 mol of morpholine, to yield N,N-bis (morpholinomethyl)imidazolidine-Z-thione, melting at 158 C.

Example 3 The numerical values of Table 2 prove the excellent properties of the vulcanizates obtained from the mixes 3 and 4, which contain accelerators of this invention, as well as the exceptional safety ensured by the new accelerators.

Example 5 The following four mixes are prepared under the usual conditions in an internal mixer. The vulcanization accelerators are finally added in a roller mixer.

TABLE 3 Mix 1 2 3 4 Parts by weight:

Neoprene W..- 100 100 Black MPG 20 20 20 Black MI- 70 7O 70 Stearic acid. 0. 75 0. 75 0.75 Octylphthalate 15 15 15 Zinc oxide 5 5 5 5 Magnesium oxide 4 4 4 4 Imidazolidine-2thione 1 1 N,Nf-bis(piperidinomethy1) imidazohdine-Z-thione 2. 9 N,Nbis(morpholinomethyl)- imidazolindine-Z-thione 2. 9'

A known accelerator used for comparison.

With each of these four mixes the scorching time according to Mooney is measured, whereupon the mixes are moulded in a press at 153 C. The scorching time and the properties of the vulcanizates are shown in the following table:

TABLE 4 scorching time Vulcanisation Tensile Modulus Elongation Shore Mix according to time in strength, 200%, at rupture hardness Mooney at minutes kg./cm. kgJcm. in percent A 110 C. in mins.

The numerical values of Table 4 likewise show the Example 7 good properties of vulcanizates prepared from mixes containing the new accelerators and their advantages insofar as the scorching safety is concerned.

The following four mixes are prepared under the usual conditions in a Banbury internal mixer, the accelerator being finally incorporated in a roller mixer.

A known accelerator used for comparison.

Example 6 TABLE 7 The following four mixes are prepared in a roller mixer I t t b Mix under the conditions conventionally employed in the elas- 111516 1611 ,1 s y weight tomcr industry. 1 2 a 4 TABLE 5 Neoprene W 100 100 100 100 7 MR glieagcgagig... 0. 0. 0. 5 0. 5 Ingredients, parts by weight M3319 m g 2 i 2 Zinc oxide; 5 5 5 5 1 2 3 4 Imidazolidine-2-thione 1 N,NGbis(iignetlggfiminomcthyhirni azoi ineiia 2.16 1 fi3-i 51aaynan i N1m(diethylammmethyb- Magnesia n 4 4 4 4 lmldazolrdmc 2 th 3. 84

%inc oxide; t h r 5 5 375 5 5 mid? ine-2- ione 0. 1

NyNflblsmimethylammw A lrnown accelerator used for comparison.

methyl)-irnidaz0lidine-2- 81 With each of these four mixes the scorching t1me acthione O.

NNqfis(dibutylaminomethyl) cording to Mooney is measured, whereupon the mixes are imidazolidine-2-ihinne 1. 44 moulded 1n apress at 153 C. The scorching time and the properties of the vulcanizates are shown in the following table:

TABLE .8

Mooney value a in minutes at O. Characteristics after Vulcanization Vulcanizing Mix time in 100 121 130 minutes Rupture, Modulus 200% Elongation Shore kgJcm. kgJcm. in percent hardness A 20 1 58 40 122 g7 (:20 Y 20 20 0 405 63 2 17 9% 6% 2 as 360 63 2 48 560 58 3 16 9 6% i 38 232 575 59 222 560 4 24 13 8% l 40 216 50 595 57 a Mooney value immediately after preparing the mix.

With each of these four mixes the scorching time ac- Example 8 cording to Mooney is measured, whereupon the mixes are moulded in a press at 153 C. The scorching time and the properties of the vulcanizates are shown in the fol- The following four mixes are prepared under the usual conditions in a Banbury internal mixer, the accelerator lowing table: 60 being finally incorporated in a roller mixer.

TABLE 6 Searching time according to Mooney in Characteristics after Vulcanlsatlon minutes 0. Vulcanizing Mix time in minutes Rupture, Modulus Elongation Shore Appearance of 121 kg./cm. 600%, in percent hardness A surface kg./cm.

1 60 No vulcanization after 60 minutes Ti """fi'io" 20 52 810 42 2 b 34 40 174 2 740 g }Shght1y granularb 19% .f 40 17 Gig P 24 a 15 a 7V 20 5 8 4 22 f 40 184 52 780 41 e =Mooney value immediately after preparing the mix.

b =Mooney value after storing the mixfor 15 days.

TABLE 9 where R and R are each selected from the class consisting of alkyl and cycloalkyl, and R may also represent a Mix hydrogen atom. Ingredients, parts by weight 4. N,N'-bis (piperidinomethyl) imidazolidine-Z-thione.

1 2 3 4 5 5. N,N-bis(morpholinomethyl)imidazoli dine 2 thione. Neoprene, 100 100 100 100 6. N,N b1s(d1methylammomethyl)lmidazohdme 2 gic a i idn 0.75 0.75 0.75 0.75 hlon 0 0 7O 0 Black 20 20 20 2O 7. N,N b1s(d1ethylam1nomethyl) imidazolidme 2 tin Octylphthalat 15 15 15 15 10 one. g fi ;3- g g g g s. N,N' bis(dibutylaminomethyl)imidazolidine-Z-thigngdaiolirgne-2rthlione "1. 1

, s th 2,16 9. N,N brs(cyclohexylam1nomethyl)1m1dazol1dme-2- N,Nnsfiigautygiminomethyb- 3 thione imi azoi inee ,84

10. N,N'-bis(Nmethyl N cyclohexylamrnomethyl) lAk 1 t df imidazolidine-2-thione.

now am em or use 01 companson' 11. A vulcanizable mix comprising a ohloroprene polymer and, as vulcanization accelerator, at least one compound of the formula: With each of these four mlxes the scorching tlme according to Mooney is measured, whereupon the mixes are moulded in a press at 153 C. The scorching time and OHz-N NCH -N the properties of the vulcanizates are shown in the 1501- H lowing table: S

TABLE 10 Scorching time according to Mooney in Characteristics after vulcanization minutes at C. Vulcanizing time in minutes Rupture, Modulus200% Elongation Shore hardkg./cn1. kg./cm. in percent ness A =M00ney value immediately after preparing the mix.

We claim: 1. A compound of the formula:

R Incl: (I311, /R

0 Hz-N N C Hz-N R2 R2 wherein R and R taken separately are each selected from the class consisting of alkyl and cycloalkyl and R may also represent a hydrogen atom, and taken together with the adjacent nitrogen may represent a heterocyclic radical.

2. A compound of the formula:

IMG 0112 wherein X represents a member selected from the class consisting of methylene and an oxygen atom.

3. A compound of the formula:

=Mooney value after storing the mix for 15 days.

where R and R taken separately are each selected from the class consisting of alkyl and cycloalkyl and R may also represent a hydrogen atom, and taken together with the adjacent nitrogen may represent a heterocyclic radical.

No references cited.

I. L. SCHOFER, Primary Examiner.

D. K. DENENBERG, Assistant Examiner. 

11. A VULCANIZABLE MIX COMPRISING A CHLOROPRENE POLYMER AND, AS VULCANIZATION ACCELERATOR, AT LEAST ONE COMPOUND OF THE FORMULA: 